a=false;
b=false;

function scroll() {
var stu = document.getElementById("a");
var std = document.getElementById("b");
var pole = document.getElementById("pole");
if (pole.scrollTop == 0) document.getElementById("a").style.backgroundPosition = 'left top';
if (pole.scrollTop > 0) document.getElementById("a").style.backgroundPosition = 'left bottom';
if (pole.scrollHeight>pole.offsetHeight) document.getElementById("b").style.backgroundPosition = 'left top';
if (pole.scrollHeight==(pole.offsetHeight+pole.scrollTop)) document.getElementById("b").style.backgroundPosition = 'left bottom';
}

function spr() {
var pole = document.getElementById("pole");
alert(pole.scrollHeight+' '+pole.scrollTop+' '+pole.offsetHeight+' '+pole.offsetTop);
}

function up() {
var pole = document.getElementById("pole");
if (pole.scrollTop > 0) pole.scrollTop = pole.scrollTop-100;
scroll();
}

function down() {
var pole = document.getElementById("pole");
if (pole.scrollHeight>pole.offsetHeight) pole.scrollTop = pole.scrollTop+100;
scroll();
}

function sungora() {
var pole = document.getElementById("pole");
if (pole.scrollTop > 0) {
if (a) {
pole.scrollTop = pole.scrollTop-2;
window.setTimeout("sungora(a)", 1);
}
}
scroll();
}

function sundol() {
var pole = document.getElementById("pole");
if (pole.scrollHeight>pole.scrollTop) {
if (b) {
pole.scrollTop = pole.scrollTop+2;
window.setTimeout("sundol(b)", 1);
}
}
scroll();
}